1. Field of Invention
This invention relates generally to a telephony multiplexed communications device for buildings with preexisting interior conventional two conductor wiring. More particularly, the invention relates to a multiplexor device that enables two, or more, line telephone service provided on two conductor analog subscriber telephony lines to be multiplexed over a single existing interior conventional two conductor wire and demultiplexed at the terminal subscriber location to two, or more, analog two conductor subscriber lines.
The problem with existing wired buildings with conventional two conductor telephony wiring is that there are often only single subscriber lines wired to specific locations in the buildings. Modern communications commonly require multiple analog terminal subscriber devices, e.g. analog telephone, facsimile, and analog computer modem devices, to be utilized concurrently at a single location interior to the building. Many older buildings were constructed at a time when a single telephone line comprised of a conventional two conductor wire was installed in only a few specific areas of the interior of the building. The modern communications user who needs two analog communications devices which can be used concurrently, is faced with the choice of installing another conventional two conductor analog telephone subscriber line through the existing interior building structure which can be both costly and possibly damaging to the interior building physical appearance. The modern communications user can also face stringent or prohibitive building codes or prohibitive historic codes if the building is categorized as a historic structure or limited alterations if enacted by community building associations regulations.
2. Discussion of Prior Art
In order to provide background information so that the invention may be completely understood and appreciated in its proper context, reference may be made to a number of prior art patents as follows:
U.S. Pat. No. 5,363,432, issued to Martin et al. is concerned with using shielded cable as opposed to, the single pair of conventional twisted unshielded two conductor wire, and broadband signals, e.g. television type signals. This patent proposes that if the telephone analog subscriber line uses a shielded cable consisting of more than one pair of wires, then one of these pair of wires and the shield element can be used to transmit a broadband type of signal into the subscriber's unit without having to add a separate coaxial type of cable commonly used in conventional broadband transmission systems.
U.S. Pat. No. 5,090,052, issued to Nakajima et. al. (Tandy Corp.) provides for a telephone system with multiple analog subscriber terminal equipment for use interior to the subscribers's building which allows multiple simultaneous calls on a single telephone line. A plurality of carrier frequencies are chosen to allow for simultaneous calls incorporating frequency modulating channels for each telephone extension. The present invention distinguishes itself therefrom by using the reducing technique of multiplexing so that two, or more, analog subscriber two conductor telephone lines supplied by the telephone service provider is transmitted over existing conventional two conductor telephone wire interior to the building and using an expanding technique of demultiplexing to provide the two, or more, separate analog two conductor subscriber lines to be connected to two unaltered standard analog subscriber terminal equipments.
U.S. Pat. No. 4,821,319, issued to Middleton et. al. and U.S. Pat. No. 4,996,709 to Heep et al. disclose devices solely concerned with intercommunications (intercom) service inside the subscriber's terminal unit, using one conventional analog two conductors subscriber line connected to the telephone service provider owned central office telephone switch. The present invention distinguishes itself by multiplexing two analog two conductor lines over one pair of conventional two conductor telephone wire preexisting and interior to the building.
U.S. Pat. No. 4,706,244, issued to Watson et al. discloses a frequency multiplexed system which couples a plurality of individual telephone sets to one analog two conductor telephone subscriber line, in which the system provides for intercommunications (intercom) calls between the telephone sets which have been designed specifically to decode the frequency multiplexed signal. This system also provides additional two conductor telephone subscriber lines and requires additional conventional two conductor telephone wiring interior to the building. The present invention distinguishes itself by multiplexing two, or more, analog two conductor lines provide by the telephone service company to the outside of the building over one pair of conventional two conductor telephone wire preexisting and interior to the building and allows subscriber's to install standard analog subscriber terminal equipment to the output two conductor terminal analog subscriber telephone lines.
U.S. Pat. No. 4,807,225, issued to Fitch discloses a frequency multiplexed system which couples a plurality of individual telephone stations to one analog two conductor telephone subscriber line, in which the system provides for telephone stations that create additional communications channels and a data channel at frequencies that do not interfere with standard analog telephone extension equipment already present. These telephone stations have been designed specifically to decode the frequency multiplexed signals. The present invention distinguishes itself by multiplexing two, or more, analog two conductor lines provided by the telephone service company to the outside of the building over one pair of conventional two conductor telephone wire preexisting and interior to the building and allows subscriber's to install standard analog subscriber terminal equipment to the output two conductor terminal analog subscriber telephone lines.
A commercially available digital two telephone line carrier system, manufactured by PairGain Technologies, Inc., provides equipment located at the central office telephone switch and typically at the subscriber terminal building telephone wire entrance to provide two analog two conductor subscriber lines over a single pair of two conductor analog telephone subscriber lines supplied by the telephone service provider exterior to the building. The present invention distinguishes itself by multiplexing two, or more, analog two conductor lines provided by the telephone service company to the outside of the building over one pair of conventional two conductor telephone wire preexisting and interior to the building and allows subscriber's to install standard analog subscriber terminal equipment to output two conductor terminal analog subscriber telephone lines. The present invention further distinguishes itself by not requiring any equipment at the telephone service provider central office switch location.
Whatever the precise merits, features, and advantages of the above cited references, none of them achieves or fulfills the purposes of the telephone subscriber line multiplexer system of the present invention.